A vehicle air conditioning system conventionally includes a compressor, a condenser, an evaporator, and an accumulator arranged as a refrigerant circuit. The compressor compresses gaseous refrigerant for delivery to the condenser, where the state of the refrigerant changes from gaseous to liquid. The liquid refrigerant then passes to the evaporator, where an air blower circulates air over the evaporator to the vehicle passenger compartment. The consequent heat transfer from the ambient air to the evaporator causes the refrigerant to change to a mostly gaseous state.
The refrigerant then passes from the evaporator to the accumulator. The function of the accumulator is to separate any remaining liquid refrigerant from the gaseous refrigerant, allowing only gaseous refrigerant to return to the compressor. The residual liquid refrigerant eventually turns to a gaseous state and is then returned to the compressor. The accumulator also provides for recovery of lubricating oil contained in the refrigerant, returning a metered amount of the oil to the inlet side of the compressor.
The accumulator normally is an upright cylindrical housing with an inlet opening formed therein and having an outlet tube with its mouth near the top of the accumulator. Refrigerant from the evaporator is introduced into the accumulator through the inlet opening, which may be in the top or in the side of the accumulator housing. Suction created by the compressor draws gaseous refrigerant out of the accumulator through the outlet tube. A desiccant is usually provided to dry the refrigerant as it circulates through the accumulator.
To prevent any liquid refrigerant from entering the outlet tube and being drawn back into the compressor, some structure is typically provided to act as a shield for the mouth of the outlet tube. For example, U.S. Pat. No. 4,768,355 to Breuhan et al., assigned to the assignee of the present invention, discloses an accumulator with a domed baffle which encloses a desiccant for drying the refrigerant. The incoming refrigerant deflects off the domed baffle and flows around the desiccant. The liquid refrigerant pools in the bottom of the accumulator. Gaseous refrigerant exits the accumulator through either of two flow paths, one through the desiccant and a filter, the second through the filter only.
U.S. Pat. No. 4,800,737 to Smith et al., also assigned to the assignee of the present invention, discloses an accumulator having dual flow paths. One of the paths passes through a filter and a pressure regulator assembly, and the other passes only through the pressure regulator assembly. The function of the alternative flow path in this design is to allow for an unrestricted passage for the gaseous refrigerant out of the accumulator in case the filter becomes clogged with contamination. The filter and pressure regulator assembly both add a measurable pressure drop in the flow path, however.
Because the incoming flow of refrigerant has a relatively high velocity, turbulence can be created when the refrigerant contacts the outlet tube shield or other structure provided as an incoming flow deflector. This turbulence may hamper the efficient separation of the liquid from the gaseous refrigerant.
It has been proposed to dampen the incoming flow by filtering the refrigerant through the desiccant, which is mounted for this purpose in the upper part of the accumulator. An example of this design is U.S. Pat. No. 4,354,362 to Schumacher et al., in which all the incoming refrigerant passes through the desiccant. With this design, the liquid level may rise in the desiccant container or in a chamber provided upstream of the desiccant container, for instance when the vehicle air conditioning system is operating under low loads. This may temporarily hinder the passage of gaseous refrigerant through the accumulator.